JP2543713B2 - Variable focal length lens barrel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable focus lens such as a zoom lens having a plurality of movable lens groups that move in the optical axis direction, and particularly to a movable lens that has slightly different moving paths from each other. The present invention relates to a lens barrel suitable for a variable focal length lens having a group.

(Prior Art) In recent years, as zoom lenses have become smaller and have higher performance, the number of movable lens groups tends to increase, and the structure of the cam for controlling the movement of the zoom lenses cannot be avoided. Absent.

However, the movement control of these lens groups is also usually given to one movable lens group by one, two or three groups of cam grooves so that the movable groups having different movement amounts can move in the same cam groove. There is no example in which the cam follower of the lens group is fitted.

Usually, in order to prevent eccentricity (tilt) from occurring in the movable lens group when controlling one movable lens group, it is often the case that two sets of cam grooves are used due to space limitations. The most stable movement control can be performed by controlling one movable lens group with three sets of cam grooves.

For example, showing the arrangement of the cam grooves when the three lens groups are movable for zooming, if the cam grooves for controlling the movement of the respective lens groups are arranged in the optical axis direction as shown in FIG. 4a, The groove interval t needs to be at least 1.5 to 2 mm or more, and the total length 1 of the cam cylinder must be increased.

When the cam grooves are arranged on the cam cylinder with the phases shifted in the angular direction as shown in FIG. 6B, the arrangement angle θ of the cam grooves on the cam cylinder becomes large, and in the case of two sets, a total of six, If a set of 3 cams is used for stable control like the above, a total of 9 cam grooves are required, which makes it impossible to construct the cam cylinder, and even if it is possible, it will be difficult to ensure accuracy. Strength becomes a problem.

Furthermore, when θ is arranged so as to be small as shown in FIG.
The rising angle β of the cam groove must be increased, which hinders the operability and increases the play in the optical axis direction, which makes the focusing unstable.

(Problems to be Solved by the Invention) The present invention is directed to a variable focal length lens such as a zoom lens in which a plurality of movable lens groups move in the optical axis direction during zooming, and in particular, a plurality of movable lenses having relatively small moving amounts. In a variable focal length lens having a group, it is possible to reduce the number of cam grooves, shorten the total length of the cam barrel, make it compact, reduce cost, and achieve high precision by securing the strength of the cam barrel. It is about trying to get a torso.

(Means for Solving the Problem) The lens barrel of the present invention is a barrel for a variable focal length lens including at least two movable lens groups having different movement paths in the optical axis direction, and is a first movable lens. A first cam follower provided in the lens group and a second cam follower provided in the second movable lens group having a different moving path in the optical axis direction from the first end surface and the first end surface facing each other. While fitting into the same cam groove with two end faces,
An urging means for urging the first movable lens group and the second movable lens group between the first movable lens group and the second movable lens group in directions opposite to each other in the optical axis direction. And the first cam follower is pressed against the first end surface and the second cam follower is pressed against the second end surface by the urging means, and the first movable lens group and the second movable lens group By moving the movable lens group along the first end surface and the second end surface of the cam groove, respectively, the first movable lens group and the second movable lens group are moved in different optical axis directions. Is characterized by.

The first cam follower and the second cam follower are respectively arranged on the first movable lens and the second movable lens with their angles, directions, and phases shifted.

(Embodiment) FIG. 3 is a movement path diagram in the optical axis direction showing an example of a movement mode of an optical system suitable for implementing the lens barrel of the present invention, in which a is wide and b is telephoto. Show.

At this time, the second movable lens group II (first movable lens group) and the third movable lens group III second movable lens group) move approximately, but the interval 1 slightly changes due to zooming.

FIG. 1 shows the second movable lens group II and the third movable lens group III.
2 is a cross-sectional view of an essential part showing the holding structure of the second movable lens group II.
The holding frame 5 and the holding frame 6 of the third movable lens group III are biased by a spring 8 in the optical axis direction. As shown in FIG. 2, in each holding frame, the cam follower 3 (first cam follower) and the cam follower 4 (second cam follower) pass through the straight guide groove 9a of the fixed barrel 9 and the cam barrel. 1
No. II group III cam groove 1b. As shown in FIG. 2, the cam followers 3 and 4 may be inserted into separate straight guide grooves 9a and 9a ', and in some cases, a dedicated pin for straight guide may be provided separately from the cam followers. It may be provided so as to be engaged with the linear guide groove of the fixed barrel. In that case, the cam follower engages with the cam groove through the burr hole.

When the cam barrel is rotated about the optical axis, the group I is given a predetermined movement in the group I cam groove 1a, the group II, the group III is the group II, and the group III cam groove 1b for zooming. It At this time II
The group 1 and group 3 cam followers 3 and 4 are fitted in the same cam groove 1b, and the holding frames are biased in the optical axis direction, so that group II is the object side end surface of the cam groove 1b (first group). End surface), the group III is controlled to move at the image-side end surface (second end surface).

At this time, in order to give different movement to the II group lens and the III group lens, the object side end surface and the image side end surface of the cam groove 1b may have different shapes, and even if they have the same shape, the arrangement angle Are different, different movements occur, and a combination thereof may be used.

The above configuration is most effective when the interlocking lens groups, that is, when the moving paths of the II group lens and the III group lens in FIG. Used for. In particular, when the zoom lens barrel is of a type in which zooming is performed manually, it is desirable to suppress the spring stroke difference to this extent in order to avoid instability in the zooming operation due to a change in operating pressure. .

(Effects of the Invention) With the lens barrel of the variable focal length lens of the present invention, the cam grooves for a plurality of lens groups can be shared in the above-described configuration, the layout of the cam grooves can be facilitated, and the cost can be reduced by reducing the number of cam grooves. It has great effects such as downsizing of the cam cylinder and improvement of strength.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing a zoom lens barrel as an embodiment of the present invention, and FIG. 2 is a development view of a cam groove portion of a cam barrel,
FIG. 3 is a configuration diagram showing an example of an optical system for carrying out the present invention, and FIG. 4 is an explanatory diagram of a conventional cam barrel. In the figure, 1 is a cam barrel, 2 is a cam follower of the first movable lens group, 3 is a cam follower of the second movable lens group, 4 is a cam follower of the third movable lens group, and 5 is a second movable lens group. II is a holding frame, 6 is a holding frame of the third movable lens group III, 8 is a spring, and 9 is a fixed barrel.

Claims (2)

(57) [Claims] 1. A lens barrel for a variable focal length lens including at least two movable lens groups having different movement paths in the optical axis direction, the first cam follower being provided in the first movable lens group. , And a second cam follower provided in a second movable lens group having a different movement path in the optical axis direction is fitted into the same cam groove having a first end surface and a second end surface facing each other. In addition, the first movable lens group and the second movable lens group are biased between the first movable lens group and the second movable lens group in directions opposite to each other in the optical axis direction. Urging means is provided to press the first cam follower against the first end surface and the second cam follower against the second end surface by the urging means, respectively. 2 movable lens groups in front A variable focal point characterized in that the first movable lens group and the second movable lens group are moved in different optical axis directions by being moved along the first end surface and the second end surface of the cam groove. Range lens barrel 2. The first cam follower and the second cam follower are arranged on the first movable lens and the second movable lens, respectively, with their angles, directions, and phases deviated from each other. A lens barrel for a variable focal length lens according to claim 1.